In modern internal combustion engines, devices are used for variably adjusting the control times of gas exchange valves, in order for it to be possible to variably configure the phase relation between the crankshaft and the camshaft in a defined angular range, between a maximum early position and a maximum late position. The device usually comprises a camshaft and a hydraulic phase setting device, by means of which a phase relation between the crankshaft and the camshaft can be changed in a targeted manner by way of feeding in or discharging pressure medium. For this purpose, the phase setting device is integrated into a drive train, via which torque is transmitted from the crankshaft to the camshaft. Said drive train can be realized, for example, as a belt drive, chain drive or a gearwheel drive.
A device of this type is known, for example, from DE 195 29 277 A1. The device comprises a phase setting device and a camshaft. The phase setting device has an output element which is arranged such that it can be rotated with respect to a drive element. The drive element is drive connected to the crankshaft. The output element and the drive element delimit a pressure space which is divided by means of an axially displaceable piston into two pressure chambers which act counter to one another. The piston is displaced within the pressure space by feeding in or discharging pressure medium from the pressure chambers. The piston has a helical toothing system which meshes with a helical toothing system of the camshaft. A targeted rotation of the camshaft with respect to the crankshaft can therefore be brought about by the axial displacement of the piston.
Furthermore, the device has a pressure accumulator which is arranged in a crankcase or a cylinder head of the internal combustion engine. During the normal operation of the internal combustion engine, the pressure accumulator is filled with pressure medium, as a rule the engine oil, by a pressure medium pump. If the system pressure which is delivered by the pressure medium pump falls below a value which is required for the functionally reliable operation of the device, the pressure accumulator is emptied into the pressure medium circuit of the internal combustion engine. Brief minimum pressure undershoots within the pressure medium system can therefore be absorbed and/or the volumetric flow can be increased.
A disadvantage of this embodiment is the great space requirement of the pressure accumulator within the crankcase or the cylinder head.